The present invention relates to a read and/or write device for reading and/or recording information from/in tracks which extend substantially parallel to each other on a record carrier which device comprises a read and/or write head for scanning the record carrier for the purpose of reading and/or recording, a positioning system for moving the read and/or write head in a direction transverse to the tracks, detection means for deriving a periodic signal from the record carrier area being scanned during a movement in said direction, which periodic signal has a frequency which is indicative of the number of tracks traversed per unit of time, and a counting circuit for determining the number of tracks traversed by counting the number of reference level crossings of the periodic signal.
A device of this type is disclosed in U.S. Pat. No. 4,106,058. for reading disc-shaped optically readable record carriers. During movement of an optical read head of this device, a periodic signal is generated which crosses a zero reference level when a track is passed and so has a frequency equal to the number of tracks passed per unit of time. This signal is the envelope of the high-frequency read signal. The number of tracks passed is determined by counting the number of zero crossings of this envelope of the high-frequency signal.
A problem occurring in the prior-art device is that the counted number of tracks passed is not always in conformity with the number of tracks actually passed, so that this information can be used only to a limited extent for controlling the radial movement of the optical read head, for example for controlling the movement performed to locate a desired track portion.